This invention relates to sports racquets, e.g. tennis, squash and racquetball and more particularly to racquets with features which attenuate or dampen the vibrations caused by impact of a ball on the grid of strings forming the hitting surface.
In stringed racquets, the impact of the ball on the grid of strings deflects the frame and grid backward and the elasticity of the system above the handle acting as a free structure induces it to vibrate after the ball rebounds. The vibration pulses initially propagated in the string grid plane are transmitted through the string connections to both the racquet frame and to the throat piece or yoke in racquets having throat pieces. Since the throat piece is fastened to the racquet frame in the racquet throat area, the throat piece vibrations induced in the throat piece from the string grid are transmitted secondarily to the frame in addition to the grid vibrations transmitted directly to the oval portion of the racquet frame. These vibrations are ultimately received in the racquet handle.
Various methods have been used heretofore to reduce objectionable racquet vibrations.
Tubular racquet frames have been filled with buckshotlike weights free to move on ball impact. Handles have been filled with a viscous fluid. Weights have been placed in holes in the frame face free to move transverse to the racquet face. The motion of the shot, fluid and weights upon impact of the racquet face with the ball is said to dampen vibrations. These proposed solutions are noisy and heavy and not effective over broad frequency ranges.
Each end of a tubular racquet frame has been passed through aligned holes in three spaced plates inside the handle. One tube end is welded to the top and bottom plates with the hole in the middle plate being a clearance hole. The other tube end is welded to the top and bottom plates with the clearance hole being in the bottom plate. The friction of the tubes against the sides of the clearance holes is said to reduce vibrations as the tubes are flexed on impact. This solution is noisy and gives a feeling of something being loose on impact.
Frames have been grooved for the placement of elastomers to cushion the pulling of the strings on the frame and hollow tube frames have been filled with plastic which are said to dampen the frame vibrations. This increases the weight markedly.
A closed hoop instead of the frame has been used for the racquet stringing and the hoop connected by four spaced elastomers to the frame or by two elastomers to the frame and one to a bar across the throat space to dampen the string plane vibrations. This produces a somewhat unsolid sensation upon striking the ball, an unpleasant appearance and an unusual balance.
Another exotic proposed solution uses cantilever structures with a natural frequency equal to the general vibration frequency of the string grid connected to the frame along the longitudinal axis near a vibration antinode to reduce vibrations. The sensitivity of this system is subject to variation with hard play and abuse and it is expensive.
Couplers have been used between adjacent strings so the different resonant frequencies of the individual strings act too dampen their individual vibrations. This tends to affect the rebound characteristics of the racquet when the ball strikes a coupler.
In one construction the mass of the throat area is decreased to move the so-called percussion center of the racquet face toward the tip which is said to also reduce vibrations somewhat. This produces a weight configuration which differs from what the player is used to.
These proposed solutions are all subject to one or more objections, some are expensive, some are subject to getting out of adjustment, some prevent proper hitting of the ball on all positions of the racquet string face, some are too heavy, in some the motion of the dampening components gives a feeling of something being loose when striking the ball, some are expensive, some unusual in appearance, and in some the vibrations are only marginally damped.
It is accordingly an object of the present invention to overcome the shortcomings of the vibration dampening racquets in the prior art.
It is a more specific object of this invention to provide an inexpensive dampening apparatus in a strung racquet that will isolate the throat piece of the racquet from the racquet frame and so dampen vibrations passing from the strings, to the throat piece, to the frame thereby dampening induced frame vibrations and vibrations passing to the handle.
It is an additional object to provide a vibration dampening racquet that does not significantly affect the weight, configuration, appearance or shape of the racquet and has no moving parts.
These and other objects and features will be disclosed from the following specification and drawings.